Sound-muffling device

ABSTRACT

A sound-muffling device for use in muffling the explosive sounds in an exhaust gas system of the type commonly employed in internal combustion engines. A length of flat metal bar is formed into a helix having a diameter to fit into an elongated conduit in the exhaust system and to be releasably fixed therein to muffle and absorb sounds from the stream of exhaust gas passing through the conduit. The length diameter and pitch of the helix are controlled to produce the desired degree of sound-muffling without producing excessive back-pressure in the engine exhaust system.

United States Patent [1 1 de Cardenas 1 1 SOUND-MUFFLING DEVIGE [76] Inventor: Ignacio de Cardenas, Box 11156 Fdz. Joncos Station, Santurce, San Juan, PR. 00910 [22] Filed: July 9, 1971 [21] Appl. No.: 161,047

[52] US. Cl. 181/36 B, 181/67 [51] Int. Cl. F0ln l/08, F01n 7/08 [58] Field of Search 181/36 B, 58, 66, 181/67, 64 A, 72

[56] References Cited UNITED STATES PATENTS 2,528,674 11/1950 Thomas 181/64 A 1,577,775 3/1926 Templeton... 181/36 B 2,014,368 9/1935 Blundell 181/67 3,105,570 10/1963 Bezemes 181/36 B 3,117,650 l/1964 Ludlow et a1. 181/36 B 3,182,748 5/1965 Wirt 181/67 3,244,254 4/1966 Compo 181/67 X FOREIGN PATENTS OR APPLICATIONS 319,626 9/1929 Great Britain 181/36 B 297,871 10/1928 Great Britain 181/67 808,437 11/1936 France 410,247 5/1934 Great Britain 265,468 6/1929 Italy 339,273 4/1936 Italy 181/67 Primary ExaminerRichard B. Wilkinson Assistant Examiner-John F. Gonzales Attorney-Beveridge & DeGrandi [57] ABSTRACT A sound-muffling device for use in muffling the explosive sounds in an exhaust gas system of the type commonly employed in internal combustion engines. A length of flat metal bar is formed into a helix having a diameter to fit into an elongated conduit in the exhaust system and to be releasably fixed therein to muffle and absorb sounds from the stream of exhaust gas passing through the conduit. The length diameter and pitch of the helix are controlled to produce the desired degree of sound-muffling without producing excessive backpressure in the engine exhaust system.

5 Claims, 4 Drawing Figures Patented Juiy 17, 1973 INVENTOR IGNACIO de CAROENAS NS NT.

Mm" 1 4 41 mam-# 1 Hl/ J m:

. v 1 2 Q E ATTORNEYS 1 SOUND-MUFFLING DEVICE BACKGROUND OF THE INVENTION 1. Field of the invention This invention relates to sound-silencing, and more specifically to an improved, efficient, and inexpensive silencer or mufi'ler to be used in the exhaust system of an internal combustion engine.

2. Description of the Prior Art It is common practice to silence or muffle the sound of an internal combustion engin by inserting a muffler in the exhaust conduit system to alter the pressure, velocity, and flow characteristics of the exhaust gases to thereby reduce and absorb the sound of the explosions from the engine which otherwise are carried and may be simultaneously resonated and/or amplified through the exhaust system. The most common of these devices are the mufflers used on automotive engines which, while they may be efficient in reducing sound, nevertheless have numerous objectionable features. Such mufflers conventionally consist of an enlarged, elongated chamber connected in the exhaust pipe system and having spaced inner and outer walls with an inlet and an outlet in the opposed ends of the chamber. The exhaust gases follow a tortuous path from the inlet to the outlet, with the space between the perforated inner and the outer wall acting as an acoustical, soundabsorbing barrier. Although there are, of course, numerous variations of this general construction, they are all relatively expensive and, at least partially because of their construction which tends to trap moisture andcorrosive materials from the exhaust gases, are notoriously short-lived in ordinary use. Also, the moreefficient of these piror art devices suffer from the further objection that they tend to create excessive backpressures and thereby reduce the efficiency of the engine. They are also very difficult to remove and replace from the conventional automotive exhaust system.

In addition to the conventional mufflers described above, attempts have also been made to muffle the sound of internal combustion engines by use of various devices introduced directly into the exhaust conduits. For example, Italian patent No. 265,468 discloses the concept of inserting a metal ribbon flow divider into the exhaust conduit of an internal combustion engine, with the flow divider being deformed in a manner to produce optimum turbulence in the exhaust gas stream to thereby reduce the sound of the engine. While this Italian patent is primarily concerned with the use of a corrugated ribbon insert which is further deformed as by folding or by twisting into a helical configuration, the patent suggests that the same purpose might be served by the use of a smooth ribbon helically twisted. The pitch of the helical ribbon is indicated as being such that the flow near the center area is almost rectilinear to produce a sucking action on the gases in the lower velocity portion of the gas channels. As might be expected, however, the creation of sufficient turbulence and gas mixing to effectively muffle the sound of a high-powered internal combustion engine will also produce a substantial back-pressure in the exhaust system which will have serious adverse effects on the operation of the engine.

SUMMARY OF THE INVENTION The foregoing and other defects of the prior art mufflers used in internal combustion engine exhaust systems are avoided by the apparatus of the present invention which employs a helicoidal insert in a conduit in the exhaust system. The length and pitch of the helical insert and the diameter of the conduit into which it is inserted are carefully coordinated with the horsepower, or size, of the engine to prduce an efficient soundmuffling effect without creating excessive backpressures on the engine. In a simplified version of the invention, the helical insert is formed to fit snugly within the forward end of a conventional automobile tailpipe, with the curvature of the pipe, for example the bend required to go above the rear axle, preventing the insert from moving longitudinally through the tailpipe. Thus, initial installation as well as subsequent replacement of the insert is greatly simplified over the conventional mufflers.

In a further embodiment of the invention, the helical insert is mounted within a tublar conduit, preferably slightly longer than the helical insert, and the helix is attached to the wall of the tubular member at one end only to accommoate differential expansion of the members. The tubular member may then be inserted directly into the exhaust system, as described above, or if preferred, connected, as by clamps, in the manner of a conventional muffler.

BRIEF DESCRIPTION OF THE DRAWINGS Further advantages of the muffler according to the present invention will be apparent from the detailed description contained hereinbelow, in combination with the drawings, in which:

FIG. 1 is an elevation view, partly in section, of a portion of a conventional automobile exhaust system incorporating a muffler according to the invention;

FIG. 2 is a sectional view, on an enlarged scale, taken on a line 2-2 of FIG. 1;

FIG. 3 is an enlarged, fragmentary, elevation view of a portion of the apparatus shown in FIG. 1; and

FIG. 4 is an elevation view, in section, of an alternate embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawings, in detail, a portion of the exhaust conduit system for conveying the exhaust gases from the exhaust manifold of a conventional automobile is indicated generally by the reference numeral 10, and includes an exhaust pipe 12 connected, as by clamp 14, to a tailpipe l6. Inserted in the aft end of the tailpipe 16 is an elongated helicoidal divider or insert 18 formed by twisting an elongated strip of smooth, flat metal bar stock having a width dimension substantially equal to the diameter of the tailpipe 16 so that the helicoidal insert 18 will fit snugly inside the cylindrical end of the tailpipe. The helicoidal insert 18 is retained in the tailpipe by a short sleeve 20 inserted into the tailpipe and fixed therein by suitable means such as screws 22. As indicated in FIG. 2, insert 18 divides the internal bore of tailpipe 16 into a pair of helical flow channels semicircular in cross-section and extending the flow length of the insert 18.

Referring again to FIG. 1, an alternate position for the insert is illustrated in phantom. In this alternate position, the insert 18 is telescoped into the forward end of the tailpipe 16 and retained in place therein by the the first curved portion thereof. In this position, the insert 18 may be removed by disconnecting the clamp 14, and telescoping the tailpipe rearwardly sufficient to disengage the exhaust pipe 12 from the foreward end thereof. The insert 18 may then be pulled forward out of pipe 16 and if desired, replaced by a new insert.

Referring now to FIG. 4, a further embodiment of the invention is illustrated, in which a helicoidal insert 28 is mounted within a tubular sleeve 30 and rigidly fixed therein at one end only as by welding at 32. The sleeve 30 is preferably slightly longer than the insert 28, with the insert being free to expand longitudinally of the conduit from the weld 32 as a result of a differential in temperature between the insert and the surrounding wall.

The sleeve 30 may be dimensioned to fit snugly within a straight length of the tailpipe 16 as indicated in FIG. 4, and be retained therein by the tubular sleeve and screws 22. Alternatively, the sleeve 30 may have its ends adapted to telescopingly receive the ends of the exhaust pipe 12 and/or tailpipe 16 (in the manner of a conventional replacement muffler) to permit the assembly to be mounted either in the position of a conventional muffler or on the aft end of a somewhat shortened tailpipe.

. It is believed that the efficiency of the muffler system of the present invention is derived from the effect of the low pitch of the helicoidal insert in destroying or breaking up the resonance of the sound flowing in the exhaust conduit, though the exact reason for this efficiency is not fully understood. Particularly, it is not understood how the relatively low pitch can be employed to break up the sound resonance without creating excessive backpressures on the engine.

While I have disclosed and described preferred embodiments of my invention, I wish it understood that I do not wish to be restricted solely thereto, but do intend to include all embodiments thereof which would be apparent to one-skilled in the art and which come within the spirit and scope of my invention.

What is claimed is:

1. An exhaust system for an internal combustion engine comprising an elongated conduit consisting of an exhaust pipe section and a tail pipe section for conveying exhaust gases from the engine exhaust manifold, and a muffler including an elongated cylindrical sleeve having an outside diameter substantially equal to the internal diameter of one of said pipe sectionsand removably mounted thereon, a helicoidal insert mounted in and dividing the interior of said cylindrical sleeve into two separate helical flow paths, said helicoidal insert being formed from an elongated strip of flat, smooth metal stock twisted into the form of a helix hav ing a diametr substantially equal to the internal diameter of said sleeve, and means rigidly connectng one end portion only of said helicoidal insert to said sleeve whereby differential thermal expansion between said sleeve and said helicoidal insert is accommodated independently of difierential expansion or relative movement between said sleeve and said one pipe section.

2. The muffler as defined in claim 1 wherein the pitch P of said helix is about one-half the diameter thereof.

3. The muffler as defined in claim 2, the further improvement wherein said sleeve is mounted in telescoping relation with the forward end of said tail pipe with the rear end of said sleeve engaging a bend in the tail pipe to prevent rearward movement through aid tail pipe beyond said bend.

4. The mufiler defined in claim 2, the further improvement wherein said sleeve is mounted in the rear end portion of said tail pipe, and comprising removable means retaining said sleeve within said tail pipe.

5. The muffler defined in claim 1, and further comprising a separate length of conduit having an open forward end connected to the discharge end of said exhaust pipe and an open rearward end connected to the open inlet of said tail pipe, and means mounting said sleeve and said helicoidal insert within said length of conduit. 

1. An exhaust system for an internal combustion engine comprising an elongated conduit consisting of an exhaust pipe section and a tail pipe section for conveying exhaust gases from the engine exhaust manifold, and a muffler including an elongated cylindrical sleeve having an outside diameter substantially equal to the internal diameter of one of said pipe sections and removably mounted thereon, a helicoidal insert mounted in and dividing the interior of said cylindrical sleeve into two separate helical flow paths, said helicoidal insert being formed from an elongated strip of flat, smooth metal stock twisted into the form of a helix having a diametr substantially equal to the internal diameter of said sleeve, and means rigidly connectng one end portion only of said helicoidal insert to said sleeve whereby differential thermal expansion between said sleeve and said helicoidal insert is accommodated independently of differential expansion or relative movement between said sleeve and said one pipe section.
 2. The muffler as defined in claim 1 wherein the pitch P of said helix is about one-half the diameter thereof.
 3. The muffler as defined in claim 2, the further improvement wherein said sleeve is mounted in telescoping relation with the forward end of said tail pipe with the rear end of said sleeve engaging a bend in the tail pipe to prevent rearward movement through aid tail pipe beyond said bend.
 4. The muffler defined in claim 2, the further improvement wherein said sleeve is mounted in the rear end portion of said tail pipe, and comprising removable means retaining said sleeve within said tail pipe.
 5. The muffler defined in claim 1, and further comprising a separate length of conduit having an open forward end connected to the discharge end of said exhaust pipe and an open rearward end connected to the open inlet of said tail pipe, and means mounting said sleeve and said helicoidal insert within said length of conduit. 